package com.spaceobj.common.core.utils;

import com.google.gson.Gson;
import org.springframework.util.ObjectUtils;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
 * RSA公钥/私钥/签名工具包
 *
 * <p>字符串格式的密钥在未在特殊说明情况下都为BASE64编码格式 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密，
 * 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全
 *
 * @author zhr_java@163.com
 * @date 2022/10/9 00:22
 */
public class RsaUtils {

    /** */
    /** 加密算法RSA */
    public static final String KEY_ALGORITHM = "RSA";

    /** */
    /** 签名算法 */
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    /** */
    /** 获取公钥的key */
    private static final String PUBLIC_KEY = "RSAPublicKey";

    /** */
    /** 获取私钥的key */
    private static final String PRIVATE_KEY = "RSAPrivateKey";

    /** */
    /** RSA最大加密明文大小 */
    private static final int MAX_ENCRYPT_BLOCK = 117;

    /** */
    /** RSA最大解密密文大小 */
    private static final int MAX_DECRYPT_BLOCK = 128;

    /** */
    /**
     * 生成密钥对(公钥和私钥)
     *
     * @return
     *
     * @throws Exception
     */
    public static Map<String, Object> genKeyPair() throws Exception {

        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(1024);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        Map<String, Object> keyMap = new HashMap<String, Object>(2);
        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);
        return keyMap;
    }

    /** */
    /**
     * 用私钥对信息生成数字签名
     *
     * @param data       已加密数据
     * @param privateKey 私钥(BASE64编码)
     *
     * @return
     *
     * @throws Exception
     */
    public static String sign(byte[] data, String privateKey) throws Exception {

        byte[] keyBytes = Base64Util.decodeFromString(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(privateK);
        signature.update(data);
        return Base64Util.encode(signature.sign());
    }

    /** */
    /**
     * 校验数字签名
     *
     * @param data      已加密数据
     * @param publicKey 公钥(BASE64编码)
     * @param sign      数字签名
     *
     * @return
     *
     * @throws Exception
     */
    public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {

        byte[] keyBytes = Base64Util.decodeFromString(publicKey);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PublicKey publicK = keyFactory.generatePublic(keySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(publicK);
        signature.update(data);
        return signature.verify(Base64Util.decodeFromString(sign));
    }

    /** */
    /**
     * 私钥解密
     *
     * @param encryptedData 已加密数据
     * @param privateKey    私钥(BASE64编码)
     *
     * @return
     *
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey) throws Exception {

        byte[] keyBytes = Base64Util.decodeFromString(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateK);
        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    /** */
    /**
     * 公钥解密
     *
     * @param encryptedData 已加密数据
     * @param publicKey     公钥(BASE64编码)
     *
     * @return
     *
     * @throws Exception
     */
    public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey) throws Exception {

        byte[] keyBytes = Base64Util.decodeFromString(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicK);
        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    /**
     * 公钥加密，直接对类对象加密 先把对象转化成JSON类型，然后转化成字符数组，然后再进行加密，最后返回加密后的字节数组
     *
     * @param obj       被加密的目标对象
     * @param publicKey 公钥
     *
     * @return 被加密对象为空，返回null，异常也返回null
     */
    public static byte[] encryptByPublicKey(Object obj, String publicKey) {

        if (ObjectUtils.isEmpty(obj)) {
            return null;
        }
        byte[] result = null;
        try {
            Gson gson = new Gson();
            byte[] objByte = gson.toJson(obj, obj.getClass()).getBytes("UTF-8");
            result = encryptByPublicKey(objByte, publicKey);
        } catch (Exception e) {
            ExceptionUtil.exceptionToString(e);
            e.printStackTrace();
            return null;
        }
        return result;
    }

    /**
     * 根据源对象、私钥解密后转化成目标对象,失败则返回null,源对象为空也返回null
     *
     * @param source     源对象
     * @param target     转化成目标对象
     * @param privateKey 解密的私钥
     * @param <T>        泛型对象
     *
     * @return 异常则返回null，源对象为空也返回null
     */
    public static <T> T decryptByPrivateKey(Object source, Class<T> target, String privateKey) {

        if (ObjectUtils.isEmpty(source)) {
            return null;
        }
        try {
            byte[] objByte = (byte[]) source;
            byte[] decodeBytes = decryptByPrivateKey(objByte, privateKey);
            String res = new String(decodeBytes, "UTF-8");
            return new Gson().fromJson(res, target);
        } catch (Exception e) {
            ExceptionUtil.exceptionToString(e);
            e.printStackTrace();
            return null;
        }
    }

    /** */
    /**
     * 公钥加密
     *
     * @param data      源数据
     * @param publicKey 公钥(BASE64编码)
     *
     * @return
     *
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {

        byte[] keyBytes = Base64Util.decodeFromString(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /** */
    /**
     * 私钥加密
     *
     * @param data       源数据
     * @param privateKey 私钥(BASE64编码)
     *
     * @return
     *
     * @throws Exception
     */
    public static byte[] encryptByPrivateKey(byte[] data, String privateKey) throws Exception {

        byte[] keyBytes = Base64Util.decodeFromString(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /** */
    /**
     * 获取私钥
     *
     * @param keyMap 密钥对
     *
     * @return
     *
     * @throws Exception
     */
    public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {

        Key key = (Key) keyMap.get(PRIVATE_KEY);
        return Base64Util.encode(key.getEncoded());
    }

    /** */
    /**
     * 获取公钥
     *
     * @param keyMap 密钥对
     *
     * @return
     *
     * @throws Exception
     */
    public static String getPublicKey(Map<String, Object> keyMap) throws Exception {

        Key key = (Key) keyMap.get(PUBLIC_KEY);
        return Base64Util.encode(key.getEncoded());
    }

}
